Federal Government Says Hybrids Are Too Quiet, Must Make Noise

A wagon-style 'Prius' hybrid vehicle, a model that will likely be subject to the new rule. Toyota has sold more than three million hybrid vehicles, a key pillar of its earnings, thanks to the global popularity of the Prius model. (Image credit: AFP/Getty Images via @daylife)

Your Prius is too quiet, at least according to National Highway Traffic Safety Administration (NHTSA) officials who announced new federal rules that will require hybrid and electric vehicles to make more noise. The agency believes that such a rule will save 35 lives and prevent 2,800 injuries per year.

Because hybrid and electric vehicles produce less sound than vehicles powered by an ordinary internal combustion engine, pedestrians may not be aware of the presence of a nearby hybrid or electric vehicle. According to the agency, this means that when a hybrid vehicle is involved in a low speed maneuver (defined as making a turn, slowing or stopping, backing up, entering or leaving a parking space, or starting in traffic), it is 1.38 times more likely than an internal combustion engine vehicle to be involved in a collision with a pedestrian and 1.33 times more likely to be involved in a collision with a cyclist. The agency assumes "that this difference in accident rates is mostly attributable to the pedestrians’ inability to detect these vehicles by hearing them during these maneuvers." As part of the rule-making process, the agency is seeking comments that question that assumption. The rule only applies at low speeds because because vehicles traveling above 18 miles per hour naturally make enough noise to be heard.

NHTSA believes that manufacturers can make their vehicles safer by installing noise-making devices on the vehicles. To further that goal, they've developed 14 sample sounds that they believe will satisfy the rule's requirement. Those sounds can be sampled in .wav format here. The agency's full 248 page report is available here.